A portable television receiver particularly suited for the youth market is a concept of the inventors, which television receiver is small enough and light enough to be easily transported by a child of nine or ten years of age and is suited for the playing of video games. In the interest of eliminating battery weight such television receiver, though portable, is normally powered by connection to electric power mains. A portable computer monitor particularly suited for the youth market, which computer monitor is small enough and light enough to be easily transported by a child of nine or ten years of age and is suited for the playing of video games, is a related concept of the inventors. Such a television set or computer monitor is termed "child-transportable" in this specification. Such a "child-transportable" television set or computer monitor is likely to be frequently moved by children apt to be careless when their thoughts are distracted by the prospect of playing video games. Protective covering of the display screen to reduce the likelihood of damage to the kinescope or liquid crystal display device during such moving (and of possible consequent injury to a child) is accordingly contemplated.
Moreover, the doors for closing over the display screen are hinged in order to facilitate the making of a portable television receiver that is "child-transportable", permitting the child to carry the receiver using handles on the left and right sides of the cabinet in a two-handed carry with the closed doors resting against the lower front torso. The portable television receiver designed particularly for the American youth market and for the playing of video games includes a supporting base for the cabinet, and a swivel-and-tilt mechanism, which not only facilitates adjusting the direction of direct viewing to suit a human viewer, but which alternatively facilitates adjusting the direction stereophonic music is radiated from the loudspeakers in the doors to suit a human listener.
U.S. Pat. No. 3,627,392 issued Dec. 14, 1971 to Finley Ruppersburg is entitled STEREO SOUND REPRODUCTION SYSTEM. Ruppersburg describes portable stereophonic-sound reproduction apparatus with a case having left-hand and right-hand swinging doors that open from the front of the case to a spread position. Loudspeakers mounted in the doors are arranged for directing stereophonic sound when the doors are opened to the spread position. The case encloses a swing-down phonograph record player with associated playback electronics.
Portable television receivers and computer monitors have used swiveled cabinets to facilitate adjusting the normal viewing direction. U.S. Pat. No. 5,243,434 issued Sep. 7, 1993 to Takashi Nodama and entitled SWIVEL DEVICE FOR A TELEVISION RECEIVER is evidence of this. The United Kingdom patent application GB 2 252 003 A of Jeong-Seop Lee and Woo-Jin Kim published Jul. 22, 1992 and entitled TURNTABLE FOR TELEVISION RECEIVER describes the use of a motorized turntable for adjusting the normal viewing direction of a television receiver provided with loudspeakers contained within the cabinet body that encloses the kinescope and positioned at the left and at the right of the kinescope viewing screen.
Large console and hutch television receivers of the past have employed doors to hide their display screens when the receivers are shut off; the doors were used primarily for cosmetic reasons, so as not to have to see the dead eye of a rasterless kinescope. At one time roll-front cabinets were common for European television receivers, the roll-front doors taking up less room when opened. Doors have also been used for cosmetic reasons in stereophonic audio systems. In U.S. Pat. No. 5,119,421 issued Jun. 2, 1992 and entitled STEREO SYSTEM CABINET WITH LOUDSPEAKER DOOR ASSEMBLY, Reime describes a stereo system cabinet with front-opening loudspeaker panels that pivot around vertical axes, which close as doors when the stereo system cabinet is not in use. The loudspeakers are mounted in the lower portions of the doors, which have their upper portions closing over a shelf that can hold a "table model" color television receiver; so the problem of the permanent magnets in the loudspeaker motors affecting the color purity of the color television receiver is not addressed. The use of doors in such large television and audio equipment is somewhat cumbersome. So, in most homes the doors tend to be left open unless the preacher or some other important guest comes to call. The tendency to close the doors but seldom and the cost of the doors, particularly when finished in fine wood veneers, has reduced the market for television receivers with doors for hiding their display screens. Making swinging cabinet doors high enough to separately cover a television display screen and loudspeakers, as Reime does, tends to make the doors heavier and more prone to warpage.
Furthermore, a problem with the stereophonic-sound reproduction apparatus provided with stereophonic loudspeakers in left-hand and right-hand swinging doors, as thusfar described, is that the movement of the cabinet body, so as to direct the stereophonic sound in a direction desired by a human listener, may result in the scratching of the surface on which the cabinet body rests. In the case of a console or hutch cabinet, which tends to be quite heavy, movement of the cabinet body may scratch a hardwood, linoleum or linoleum-tile floor that supports the cabinet body. In the case of portable stereophonic-sound reproduction apparatus, its movement so as to direct the stereophonic sound in a direction desired by a human listener may scratch the top of the table or desk that supports the cabinet body. While the portable stereophonic-sound reproduction apparatus is less heavy in weight than stereophonic reproduction apparatus in a console or hutch cabinet, the table or desk that supports the cabinet body may have a fine-furniture finish that is more apt to be scratched than a hardwood floor.
Doors are not used primarily for cosmetic purposes in portable television receivers or computer monitors that embody the present invention. Rather, the doors are designed so that they can be transported by a child and are used primarily for protecting the display screens during transport in order to reduce the likelihood of damage to the kinescopes or liquid crystal display devices (and of possible consequent injury to the child). The smaller size of these doors avoids their being cumbersome, even though they are front-opening hinged doors, rather than roll-front doors. When the left- and right-swinging doors that can close over the display screen and include stereophonic loudspeakers in the doors, are opened to a spread position, the stereophonic loudspeakers flank the display screen, rather than being located below the television receiver display screen.
Stereophonic sound is provided for some television broadcasts and for some video games, and there is a problem with separating the loudspeakers of a portable television receiver sufficiently to achieve directional sound reproduction. Satellite loudspeakers connected by cabling to the portable television receiver can be used to overcome this problem. However, the satellite loudspeakers interfere with ready portability, are likely to be lost by a child during transport, and contribute to the cluttering up of the household by child's play. The mounting of the stereophonic loudspeakers in doors opening to the left and to the right of the display screen provides separation sufficient to achieve directional sound reproduction for a child seated close to the portable television receiver, close seating being normal with the small screen sizes associated with a receiver small enough to be transported by a child. Hinged doors, including a left door hinged from the cabinet for covering the left-hand side of the display screen when closed and for extending from the left-hand side of the cabinet when opened, and including a right door hinged from the cabinet for covering the right-hand side of the display screen when closed and for extending from the right-hand side of the cabinet when opened, not only protect the kinescope or liquid crystal display device during transport. During transport, such doors also protect the loudspeakers mounted on the insides of those doors as closed over the display screen.
In U.S. Pat. No. 2,547,447 issued Apr. 3, 1951 and entitled APPARATUS FOR STEREOPHONIC SOUND REPRODUCTION, de Boer describes the mounting of stereophonic loudspeakers on right and left sliding doors of a stereophonic radio receiver. In de Boer's apparatus, the loudspeakers are mounted to have their openings on the outside of the right and left sliding doors as closed over the radio receiver, which tends to leave the loudspeakers inadequately protected during transport. For example, when transport is from one building to another during a rainstorm, water is likely to enter the speaker opening. Mounting the loudspeakers on the insides of hinged doors that close over the display screen can provide protection from such event, since the cabinet and doors of a child-transportable television receiver or computer monitor generally will be made of an engineering plastic material impervious to water.
The mounting of loudspeakers in doors covering the display screen of a television receiver during transport involves considerations not encountered by de Boer or Reime, concerning the interaction of magnetic fields emanating from the loudspeakers magnetizing metal components near the display screen when the doors are closed over the display screen, it is here pointed out. Permanent magnets in the drive motors of the loudspeakers distort the magnetic conditions near the faceplate of a color kinescope, for example. Magnetization of metal components near the display screen creates local magnetic fields that affect the landing of the electronic beams on a pattern of display-screen phosphors creating color purity problems.
As is well known to the designers of color television receivers, the shadow mask or aperture grill within a kinescope is commonly made of ferrous metal and is subject to magnetization when exposed to magnetic fields, even such weak ones as the earth's magnetic field. Any change in such magnetization, such as occurs during the changing of the television receivers position within the earth's magnetic field, affects the deflection of the three electron beams that respectively scan red-emitting phosphors, green-emitting phosphors and blue-emitting phosphors in the display screen, leading to a loss of proper color registration that is quite objectionable to human viewers. To counter such loss of color registration and maintain color purity, the color kinescope is commonly provided with built-in degaussing coils that, when the television receiver has its power first turned on after being off for some time, are briefly energized for de-magnetizing the shadow mask or aperture grill. Powering up of the receiver before the doors over the display screen are opened up and locked or left in an open position interferes with the automatic de-gaussing coil removing magnetic field anomalies near the display screen induced by magnetic fields emanating from the loudspeakers, however, it is here pointed out. Accordingly, if an aperture grill color kinescope, shadow mask color kinescope, or related type of color kinescope is used as the display device in a child-transportable television receiver or computer monitor, equipped with loudspeakers in doors hinged to close over the display screen, the automatic de-gaussing should be deferred until after the doors are opened up and locked or left in an open position, it is here pointed out. This can be done, also deferring the application of power to the television receiver or computer monitor until the doors are opened up and locked or left in the open position, it is here pointed out.
The color purity problems posed by including loudspeakers in doors hinged to close over the display screen can be mitigated or avoided in other ways, it is here pointed out. The use of non-magnetic materials in the aperture grill or shadow mask, the chassis and the kinescope mounts reduces color purity problems supposing an aperture grill color kinescope, shadow mask color kinescope, or related type of color kinescope is used as the display device. The use of engineering plastics in a child-transportable television receiver or computer monitor is attractive anyway for reducing weight and for providing resistance to damage resulting from accidental dropping or banging against other objects. The loudspeaker motors can be constructed to avoid the use of permanently magnetized structures, being constructed entirely using electromagnetic structures. Indeed, the motors of the loudspeakers in the doors can be of an electrostatic type rather than an electromagnetic type, better to avoid magnetic structures. Since small electrostatic loudspeakers with good lower frequency response are a problem, the loudspeakers in the doors can be aided by a lower-frequency-response loudspeaker of electromagnetic type located in the main body of the cabinet or in a base therefor. The color purity problems can be avoided by replacing the standard color kinescope with another color display device, such as a liquid crystal color display device, or such as a single-gun kinescope using controlled-penetration phosphors, which can be of "onion-skin" type by way of example. A more conventional color kinescope is favored, however, because of its lower cost.
The stereophonic loudspeakers in display-screen doors concept used in the portable television receiver particularly suited for the youth market appears to be so attractive that the concept is being extended across a full line of color television receivers for the American market including non-portable table-top receivers and stand-on-the-floor console receivers. The concept will also be employed in computer monitors. American television receivers are peculiar in their styling compared to television receivers in the rest of the world. Rather than using flush mounting of the kinescope screens in their cabinetry, which is common in the rest of the world, especially Europe, American television receivers and computer monitors usually have their kinescope screens mounted behind a bezel that forms a "picture frame" for the human viewer, which American customers prefer.
The portable television receiver designed particularly for the American youth market and for the playing of video games uses a kinescope with a flat face and a deep surrounding bezel, to reduce incident light falling on the screen during daytime play, and to give the child the feeling he was in his own world secured from the intrusion of adults. A possible mitigation of the problem of the shadow mask or aperture grill of the kinescope being magnetized by the permanent magnets in the motors of the door-mounted loudspeakers was another factor in evaluating a deep-bezel design in premarketing studies of possible cabinet design. A kinescope driven from portable television electronics already in production and using conventional de-gaussing procedures when the television receiver has its power first turned on after being off for some time was used in the pilot deep-bezel-design television receiver.
Surprisingly, when the pilot deep-bezel-design television receiver was operated, there was no evidence of the expected problem of the shadow mask or aperture grill of the kinescope being magnetized by the permanent magnets in the motors of the door-mounted loudspeakers, solutions to which problem are noted above. In retrospect, this appears to be because the magnetic flux leakage from modern loudspeaker motors is kept quite small by the high permeability of the materials used in the permanent magnets to keep motor weight down and by the magnetic structures employed. The paths of the loudspeakers when swung toward the screen are retraced when the doors are opened, so the resultant change in the magnetic field tends towards being zero. Simply using a bezel and door design in which the permanent magnets in the motors of the door-mounted loudspeakers are held a few centimeters from the face of the kinescope screen avoids the problem of the shadow mask or aperture grill of the kinescope being magnetized sufficiently to affect color purity noticeably.
Furthermore, the pilot deep-bezel-design television receiver used a monophonic low-frequency-range loudspeaker, or "woofer", that was mounted in the television receiver cabinet at some location removed from the kinescope screen. Human beings detect stereophonic separation effects primarily at mid frequencies, particularly when loudspeaker separation distances are less than four or five feet. Since stereophonic separation effects at low frequencies are not pronounced, the use of a monophonic woofer when loudspeaker separation distances are constrained to less than four or five feet is common in less-expensive stereophonic reproduction systems, particularly, those of console type. In order to maintain acoustic coupling at low frequencies to the room in which the listener is positioned, woofers generally have larger surfaces (cones) to be driven by their motors than loudspeakers for higher frequencies do. In order that woofers can drive these larger surfaces, the permanent magnets in the motors of woofers are commonly larger and of greater field strength than the permanent magnets in the motors of mid-frequency-range loudspeakers or in the motors of certain types of high-frequency-range loudspeakers, or "tweeters". Not having woofers in the doors of the pilot deep-bezel-design television receivers helps avoid the problem of the shadow mask or aperture grill of the kinescope being magnetized sufficiently to affect color purity noticeably. This permits the bezel depth in a deep-bezel-design television receiver to be made shallower, without incurring loss of color purity owing to kinescope magnetization by the loudspeaker motors.
Other factors are considered in the design of a child-transportable television receiver or computer monitor. To keep the cabinet weight down to facilitate transportation by a child, a design without 50/60 Hz power transformer is used. The cabinet exclusive of its hinged doors over the display screen completely surrounds that portion of the apparatus used for generating the images on the display screen, and is free from voids that would allow the insertion of objects into the chassis that would pose an electric shock hazard. The cabinet is preferably designed to encourage two-handed carrying by the child, with the display screen doors against the stomach of the child. This lessens the chance of injury during lifting and reduces the likelihood of dropping the apparatus or of banging its cabinet into other persons or objects. Carrying handles, if they are provided, are preferably on the sides of the cabinet or underneath the cabinet to discourage one-handed carrying by the child. The cabinet when closed for carrying by a child is designed with large-radius rounded corners to reduce the likelihood of the child injuring himself, another child, doorways or walls of a house, furniture in a house, or a vehicle. Yielding or cushioned surfaces on the cabinet are preferable, if cost considerations can be met. The hinges on the cabinet doors and any locking mechanisms on the doors are designed to avoid the possibility of pinching fingers or other body parts.
The hinges on the cabinet doors are of such sturdy construction that the cabinet doors cannot be torn off the cabinet. If the hinges use hingepins (being of piano type, for example, the ends of each hinge are provided with guards to forestall the hingepin being extracted by a child. The conduction of electric driving signals to the loudspeakers in the doors should be done such that the conductors are not easily susceptible to a child's tampering. The power cord is preferably retractable into the cabinet during transportation of the child-transportable television receiver or computer monitor. Apparatus to play a prerecorded "pull the plug" reminder message can be included in the child-transportable television receiver or computer monitor and actuated by the child lifting the receiver or monitor from a position of rest. The apparatus to play the reminder message can be similar to that used in some toys (such as talking dolls, for example).